1. Technical Field
The present invention relates to a cleaning device of a liquid jet apparatus, a liquid jet apparatus, and a cleaning method.
2. Related Art
An ink jet recording apparatus is widely known as an example of liquid jet apparatuses. The ink jet recording apparatus includes a recording head ejecting (discharging) ink droplets (liquid) so as to perform recording (printing) and the thickness of the recording medium used such as sheets of paper to be recorded (printed) varies depending on the purposes the recording medium. The liquid droplets are ejected onto the recording medium from a recording head that moves across the recording medium. Therefore, as the thickness of the used recording medium is changed, the gap between the recording head and the surface of the recording medium is changed accordingly and the landing positions of the liquid droplets are displaced, thereby deteriorating printing accuracy. JP-A-11-115275 and JP-A-2002-264350 disclose a recording apparatus including a platen gap adjusting device which suitably adjusts the gap (platen gap) between the recording head and a platen (a sheet guiding member) by moving the recording head in a vertical direction depending on the thickness of the recording medium.
The ink jet recording apparatus includes a cleaning device which performs a wiping function of wiping the nozzle forming surface (a surface having nozzle orifices) of a liquid jet head and removing dirty ink, a flushing function of flushing out the ink clogged in the nozzles by means of an idle discharging operation, and a sucking function of forcibly sucking the ink from the nozzles so as to prevent the ink clogged in the nozzles (see JP-A-11-115275, JP-A-2002-264350, and JP-A-2003-127434). The cleaning device includes a strip-like wiping member formed of an elastic material and a capping unit which covers the nozzle forming surface of the recording head in order to prevent the nozzles from drying. When a sucking operation is performed, the capping unit covers the nozzle forming surface so as to seal the nozzle forming surface and a suction pump applies a negative pressure to a sealed space, thereby forcibly discharging the liquid from the nozzles of the recording head. The sucking operation is generally followed by a wiping operation of removing the liquid attached to the nozzle forming surface and rearranging liquid meniscuses formed at the nozzle orifices.
However, when the position of the recording head is adjusted in a vertical direction using the platen gap adjusting device, the gap between the vertical position of the recording head and vertical positions where the capping unit and the wiping member are positioned at the time of cleaning varies accordingly. As the gap varies, the contact degree (the amount of interference) of the wiping member with respect to the nozzle forming surface of the recording head changes accordingly. As a result, the operation of wiping the nozzle forming surface fails or the ink is scattered into the recording apparatus when the elastically deformed wiping member recovers its original shape by an elastic recovery force, thereby contaminating the recording apparatus.
In order to solve the above-mentioned problems, JP-A-11-115275 discloses a technology in which at a cleaning period, the wiping member is automatically adjusted by the platen gap adjustment device so as to obtain a platen gap different from that of a printing period and a predetermined amount of interference with respect to the nozzle forming surface.
JP-A-2002-264350 discloses an ink jet recording apparatus in which the amount of interference between the wiping member and the recording head varies depending on the size of the platen gap and the speed or the number of wipings is changed depending on the size of the platen gap when the wiping performance deteriorates due to the interference, thereby performing a desirable cleaning operation
JP-A-2003-127434 discloses a cleaning device in which the capping unit and the wiping member are integrated so as to rise and fall as a single member. In this case, since the amount of interference between the wiping member and the recording head also varies in accordance with the adjustment of the platen gap, it is possible to suitably adjust the amount of interference between the wiping member and the recording head by utilizing the arrangement disclosed in JP-A-11-115275 or to suitably perform the cleaning operation of the wiping member by utilizing the method disclosed in JP-A-2002-264350.
In JP-A-2002-264350, since the amount of interference between the wiping member and the recording head varies depending on the size of the platen gap, the cleaning performance can be enhanced by modifying the speed or the number of wipings. However, as the size of the platen gap varies, the distance between the capping unit and the recording head as well as the amount of interference may vary. For example, when a thick sheet is used for printing and the recording head is positioned at a relatively high position in order to obtain a wide platen gap, the gap between the recording head and the capping unit widens when a flushing operation is performed. When the gap between the recording head and the capping unit widens and the distance from the nozzles to the capping unit at which the liquid droplets discharged from the nozzles are dropped increases, the liquid droplets discharged from the nozzles are likely to become mist and freely fly into the recording apparatus, thereby contaminating the recording apparatus. This problem may also arise in the cleaning device disclosed in JP-A-2003-127434 in which the capping unit and the wiping member are integrated into a single member.
In addition, in JP-A-11-115275, since the platen gap is automatically adjusted, the wiping member has a predetermined contact degree (the amount of interference) with respect to the nozzle forming surface during the cleaning operation. However, the platen gap needs to be changed to a platen gap different from that of the printing operation for every wiping period, thereby decreasing the throughput of the printing device. A method of changing the platen gap every cleaning period may be applied to the flushing operation. Like the case of the wiping period, the platen gap needs to be changed to a platen gap different from that of the printing operation for every flushing period, thereby decreasing the throughput of the printing device. In addition, the method of changing the platen gap every cleaning period cannot be applied to the recording apparatus disclosed in JP-A-2003-127434 which includes a platen gap adjusting device that is manually operated.